A visible light modulator for high-speed optical communication and optical computing

Abstract

The present invention is related to the field of optical systems, specifically a visible light modulator for high-speed optical communication and optical computing, comprising: a modulator substrate, a thin film optical waveguide layer, an input optical waveguide, an output optical waveguide, an optical distribution device, a plurality of photodetectors, a radio frequency electrode, and a bias electrode. This modulator effectively improves the modulation efficiency and response speed of optical signals; greatly improves the bandwidth and modulation efficiency of the modulator; reduces the loss problem existing in traditional mode conversion, and significantly improves the optical signal transmission efficiency and system reliability.

Description

Technical Field

[0001] The present invention relates to the technical field related to optical systems, and in particular to a visible light modulator used for high-speed optical communication and optical computing. Background Art

[0002] In the field of modern optical communications and optical computing, the research and development of high-speed visible light modulators is crucial. These modulators usually use nonlinear materials such as lithium niobate (LiNbO3), potassium dihydrogen phosphate (KDP), potassium titanium phosphate (KTP) or barium titanate (BaTiO3) to achieve high-efficiency and high-speed optical signal modulation. High-speed visible light modulators based on the electro-optical effect of these materials have demonstrated excellent modulation capabilities in the visible light band and can effectively cope with the rapidly growing data transmission and processing needs.

[0003] High-speed optical modulation technology not only greatly improves the bandwidth and efficiency of data transmission, but also promotes the development of optical communication systems, especially in the fields of optical fiber networks, optical computing and high-speed Internet infrastructure. In addition, high-speed optical modulation technology may also play a core role in advanced applications such as quantum computing and medical imaging.

[0004] However, the performance of these devices in the visible light band still has certain limitations.

[0005] Specifically, traditional silicon-based photonic devices have large losses in the visible light band, and although modulators based on III-V materials have improved performance, their preparation costs are relatively high, and there is also a problem of poor compatibility with existing silicon-based technology modulators.

[0006] Based on this, the development and optimization of high-speed optical modulators in the visible light band is particularly necessary for the development and improvement of communication technology. Summary of the invention

[0007] The present invention proposes a high-speed visible light modulator based on thin-film electro-optical materials to address the problems of large loss in current silicon-based modulators and high cost and poor compatibility with existing silicon-based modulators despite improved performance of III-V group materials. The present invention significantly improves the performance and integration of the modulator through innovative device structure and manufacturing process. The modulator not only has the advantages of high modulation bandwidth and low insertion loss, but is also compatible with existing silicon-based photonic technology, providing important technical support for future efficient visible light communication systems.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A visible light modulator for high-speed optical communication and optical computing, comprising:

[0010] The modulator substrate provides structural support and serves as an integration platform for the various optoelectronic components;

[0011] A thin film optical waveguide layer, arranged on a modulator substrate, is provided with coplanar waveguide electrodes and modulates an optical signal by applying an electric field;

[0012] An input optical waveguide, used for inputting an optical signal;

[0013] an output optical waveguide for guiding the modulated optical signal;

[0014] An optical distribution device, used for distributing an optical signal entering from an input optical waveguide to a plurality of modulation channels to achieve parallel processing;

[0015] Several photodetectors are arranged at the output of each modulation channel to monitor the modulated optical signal and conduct real-time performance evaluation;

[0016] A radio frequency electrode, applying a modulation voltage to control the electro-optical response characteristics of the electro-optical material;

[0017] Bias electrodes are used to change the refractive index in the interferometer arms, adjust the optical path difference to achieve precise phase modulation and intensity regulation of the output signal, and balance the interferometer and adjust the bias point to ensure it operates in the optimal state.

[0018] Preferably, the optical distribution device is an optical splitter or an arrayed waveguide grating demultiplexer. The arrayed waveguide grating (AWG) demultiplexer is suitable for wavelength multiplexing (CWDM) applications.

[0019] Preferably, the coplanar waveguide electrode includes a signal electrode and a ground electrode.

[0020] Preferably, the electrode structure of the visible light modulator adopts a periodically loaded coplanar slot waveguide electrode structure. The coplanar slot waveguide electrode optimizes radio frequency (RF) parameters by adjusting slot parameters to ensure high modulation efficiency and impedance matching.

[0021] Preferably, the input optical waveguide and the output optical waveguide use two-stage inverse tapered tip couplers for mode conversion.

[0022] Preferably, the tip width of the inverse cone coupler is 100-700 nm, and is used for mode conversion between optical fiber and thin film optical waveguide.

[0023] Preferably, the thin-film optical waveguide layer has an electro-optical material thin film, performs a modulation function of the optical signal, and its electro-optical response characteristics are controlled by a modulation voltage applied by a radio frequency electrode.

[0024] Preferably, the electro-optic material film is one of lithium niobate, potassium dihydrogen phosphate, potassium titanium phosphate, electro-optic polymer and barium titanate.

[0025] Preferably, the material of the optical waveguide in the thin film optical waveguide layer is silicon nitride, silicon or polymer.

[0026] Preferably, the visible light modulator further comprises a covering layer covering the thin film electro-optic material layer and the coplanar waveguide electrode, and the material of the covering layer is silicon dioxide (SiO2) or a polymer.

[0027] In the visible light band, the choice of photonic devices is critical to the performance of the overall system. Traditional silicon-based photonic devices face significant challenges in this band, especially in terms of optical losses. Due to the high absorption and scattering losses of silicon in the visible light band, this leads to reduced efficiency in practical applications. In addition, the band gap of silicon materials limits its application to shorter wavelengths, further restricting its use in the visible light band.

[0028] To solve these problems, researchers turned to III-V compound semiconductor materials, such as gallium arsenide (GaAs) and indium phosphide (InP). These materials have better optical properties in the visible light band, including lower absorption loss and better refractive index control capabilities. Modulators made of III-V materials have significant improvements in key performance indicators such as modulation rate, modulation depth and optical loss.

[0029] However, despite the excellent performance of III-V materials, their application also faces major challenges. First, the preparation cost of III-V materials is relatively high. Its growth and processing technology is complex, involving extreme conditions such as high temperature and high pressure, as well as strict control of crystal structure, which increases production costs. In addition, these materials usually need to be grown on foreign substrates, further increasing manufacturing complexity.

[0030] Preferably, the visible light modulator comprises:

[0031] Modulator substrate,

[0032] A cladding layer is prepared on the modulator substrate and is used to cover the supporting thin film optical waveguide;

[0033] Thin film optical waveguide: coated in the above coating layer;

[0034] Electro-optical material film: bonded on the above-mentioned cladding layer, used to carry the coplanar waveguide electrode;

[0035] Coplanar waveguide electrode: attached to the thin film electro-optic material layer, modulating the optical signal by applying an electric field;

[0036] The distance between the thin film optical waveguide and the lower surface of the thin film electro-optical material layer is less than 100 nm.

[0037] This is an optimized solution for the basic solution. The cladding layer covers the optical waveguide. The distance between the thin-film optical waveguide and the lower surface of the thin-film electro-optical material layer is less than 100nm. This distance makes it easy for the optical mode field in the optical waveguide to be coupled to the thin-film electro-optical material layer.

[0038] The new design structure adopted by the present invention solves the loss problem existing in the traditional mode conversion and significantly improves the optical signal transmission efficiency and system reliability.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The modulator provided by the present invention effectively improves the modulation efficiency and response speed of the optical signal;

[0041] The modulator provided by the present invention greatly improves the bandwidth and modulation efficiency of the modulator;

[0042] The modulator provided by the present invention reduces the loss problem existing in traditional mode conversion and significantly improves the optical signal transmission efficiency and system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A top view of a visible light modulator integrated with an optical splitter and a photodetector provided by the present invention is provided.

[0044] Figure 2 A top view of a multi-channel visible light modulator integrated with an arrayed waveguide grating demultiplexer and a photodetector provided by the present invention is provided.

[0045] Figure 3 Shown is a cross-sectional view of an exemplary thin film light guide suitable for use in a visible light modulator of the present invention.

[0046] Figure 4 Shown is a cross-sectional view of another exemplary thin film light guide suitable for use in a visible light modulator of the present invention.

[0047] Figure 5 Shown is a cross-sectional view of another exemplary thin film light guide suitable for use in a visible light modulator of the present invention.

[0048] Figure 6 Shown is a cross-sectional view of another exemplary thin film light guide suitable for use in a visible light modulator of the present invention.

[0049] Figure 7 A cross-sectional view of a visible light modulator provided in an embodiment of the present invention is provided.

[0050] Figure 8 A three-dimensional schematic diagram of a visible light modulator provided in an embodiment of the present invention is given.

[0051] Fig. 9 The given is Figure 8 A side view of a visible light modulator provided in FIG.

[0052] Fig.10 The given is Figure 7 The optical mode field distribution of the visible light modulator provided in at multiple different wavelengths.

[0053] Fig.11 The given is Figure 7 A graph showing the relationship between the half-wave voltage (Vπ) and the modulator length (L) of a visible light modulator is provided in FIG.

[0054] Fig.12 The given is Figure 7 The frequency response diagram of the visible light modulator provided in the figure shows the ideal load and signal source impedance matching without RF loss.

[0055] Fig.13 Provided is a schematic structural diagram of a visible light modulator based on a coplanar slot waveguide electrode structure provided by the present invention.

[0056] Fig.14 The given is Fig.13 Equivalent circuit model diagram of the coplanar slot waveguide design described in FIG.

[0057] Fig.15 Given are the electro-optical response characteristics of lithium niobate thin film optical waveguide modulators using different electrode designs.

[0058] In the figure: 100 thin film substrate, 101 electro-optic material thin film, 102 thin film optical waveguide, 103 cladding layer, 104 signal electrode, 105 ground electrode, 106 first glass cladding layer, 107 electro-optic polymer layer, 108 second glass cladding layer, 109 first inverse tapered tip waveguide coupler, 110 second inverse tapered tip waveguide coupler;

[0059] 200 modulator substrate, 201 input optical waveguide, 202 output optical waveguide, 203 optical splitter, 204 photodetector, 205 radio frequency electrode, 206 bias electrode, 207 arrayed waveguide grating demultiplexer. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0061] It should be noted that the terms "first", "second", etc. used in the description of the present invention, the claims, and the above-mentioned drawings are used to distinguish similar objects rather than to describe a specific order or priority order. It should be understood that such data can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, it is not required to explicitly list those steps or units of a process, method, system, product, or device that includes a series of steps or units, and other steps or units that are not explicitly listed or inherent in these processes, methods, products, or devices may also be included.

[0062] In the present invention, the terms "bonding", "thin film", "preparation" and the like should be understood in a broad sense. For example, the term "bonding" can be eutectic bonding, surface activated bonding or interlayer bonding. Similarly, the term "thin film" can be a spin-coated film, a deposited film or a thinned film. Furthermore, the term "preparation" can be prepared by chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD) or magnetron sputtering. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0063] It should be noted that the embodiments and features of the present invention can be combined with each other without conflict. The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0064] Example:

[0065] The present invention provides a visible light modulator for high-speed optical communication and optical computing, comprising:

[0066] The modulator substrate provides structural support and serves as an integration platform for the various optoelectronic components;

[0067] A thin film optical waveguide layer, arranged on a modulator substrate, is provided with coplanar waveguide electrodes and modulates an optical signal by applying an electric field;

[0068] An input optical waveguide, used for inputting an optical signal;

[0069] an output optical waveguide for guiding the modulated optical signal;

[0070] An optical splitter, used for distributing an optical signal entering from an input optical waveguide to a plurality of modulation channels to achieve parallel processing;

[0071] Photodetectors, which monitor the modulated optical signal for real-time performance evaluation;

[0072] A radio frequency electrode, applying a modulation voltage to control the electro-optical response characteristics of the electro-optical material film;

[0073] Bias electrodes are used to change the refractive index in the interferometer arms, adjust the optical path difference to achieve precise phase modulation and intensity regulation of the output signal, and balance the interferometer and adjust the bias point to ensure it operates in the optimal state.

[0074] The optical splitter is an array waveguide grating (AWG) demultiplexer, which is suitable for wavelength multiplexing (CWDM) applications.

[0075] The coplanar waveguide electrode includes a signal electrode and a ground electrode, and the signal electrode and the ground electrode are connected through an inverse cone coupler.

[0076] The electrode structure of the visible light modulator adopts a periodically loaded coplanar slot waveguide electrode structure. The coplanar slot waveguide electrode optimizes radio frequency (RF) parameters by adjusting slot parameters to ensure high modulation efficiency and impedance matching.

[0077] The input optical waveguide and the output optical waveguide use a two-stage inverse tapered tip coupler for mode conversion.

[0078] The tip width of the reverse cone coupler is 100-700nm and is used for mode conversion between optical fiber and thin film optical waveguide.

[0079] The thin film optical waveguide layer has an electro-optical material thin film, performs the modulation function of the optical signal, and its electro-optical response characteristics are controlled by the modulation voltage applied by the radio frequency electrode.

[0080] The thin film electro-optic material layer is one of lithium niobate, potassium dihydrogen phosphate, potassium titanium phosphate, electro-optic polymer and barium titanate.

[0081] The material of the optical waveguide in the thin film optical waveguide layer is silicon nitride, silicon or polymer.

[0082] The visible light modulator further comprises a covering layer covering the thin film electro-optic material layer and the coplanar waveguide electrode, wherein the covering layer is made of silicon dioxide (SiO2) or a polymer.

[0083] like Figure 1 As shown, this is a top view of a visible light modulator that integrates an optical splitter and a photodetector.

[0084] The modulator consists of several key components and their layout:

[0085] The modulator substrate is a silicon substrate, which provides structural support and serves as an integration platform for various optoelectronic components;

[0086] The optical splitter is responsible for distributing the optical signal entering from the input optical waveguide to multiple modulation channels to achieve parallel processing;

[0087] The bonded electro-optic material thin film layer performs the modulation function of the optical signal, and its electro-optical response characteristics are controlled by the modulation voltage applied by the radio frequency electrode;

[0088] Bias electrodes are used to change the refractive index in the interferometer arms, adjust the optical path difference to achieve precise phase modulation and intensity regulation of the output signal, and balance the interferometer and adjust the bias point to ensure it operates in the optimal state;

[0089] The detection photodetector monitors the modulated optical signal for real-time performance evaluation.

[0090] The output optical waveguide is responsible for guiding the modulated optical signal.

[0091] The input optical waveguide and the output optical waveguide can be optionally Fig.14 A two-stage inverse tapered tip coupler is shown in Figure 1 to optimize the light coupling efficiency and reduce insertion loss.

[0092] This design achieves efficient distribution, precise modulation, and real-time monitoring of optical signals by integrating optical splitters and photodetectors, and is suitable for optical communication systems and optical computing devices for high-density optical signal processing. This platform has a wide range of potential applications, including but not limited to: photonic switching networks for neuromorphic or quantum computing, devices for quantum state conversion from microwaves to photons, integrated electro-optical frequency comb sources, on-chip generation of second harmonics and compressed light, and high-speed electro-optical devices for optical communications or rapidly tuned low-noise lasers. These applications not only demonstrate the versatility of the technology of the present invention, but also highlight its important role in promoting the development of future high-performance optoelectronic systems.

[0093] like Figure 2 As shown, Figure 2 A top view of a multi-channel visible light modulator integrated with an arrayed waveguide grating demultiplexer and a photodetector provided by the present invention is provided.

[0094] The design and Figure 1 Basically the same, except the splitter is replaced by an arrayed waveguide grating demultiplexer (AWG) for close wavelength multiplexing (CWDM) applications.

[0095] The specific components are as follows:

[0096] The modulator substrate is a silicon substrate, which provides structural support and serves as an integration platform for various optoelectronic components;

[0097] AWG demultiplexer, which separates the optical signal of the input optical waveguide into multiple modulation channels;

[0098] The electro-optic material film performs the modulation function of the optical signal, and its electro-optical response characteristics are controlled by the modulation voltage applied by the radio frequency electrode;

[0099] Bias electrodes, used to change the refractive index in the interferometer arms, adjust the optical path difference to achieve precise phase modulation and intensity regulation of the output signal, and balance the interferometer and adjust the bias point to ensure it operates at its optimal state;

[0100] A photodetector for detection, which monitors the modulated optical signal for real-time performance evaluation;

[0101] The output optical waveguide is responsible for guiding the modulated optical signal.

[0102] This design achieves efficient separation, precise modulation and real-time monitoring of optical signals by integrating AWG demultiplexers and photodetectors, and is suitable for high-density optical signal processing systems with wavelength multiplexing. The advantage of the present invention lies in its hybrid integration of different material platforms, which achieves optimal power, performance and cost partitioning. Through this optimized partitioning, the overall cost of the system can be significantly reduced while ensuring high performance. In addition, the design provides extremely wide design freedom, allowing customized design according to specific application requirements. Another significant advantage is the use of thermally stable waveguides that support multi-channel scalability. This thermally stable waveguide can maintain stable performance under different temperature conditions, ensuring the reliability and scalability of the system, and is very suitable for large-scale and high-density optical communication applications.

[0103] Regarding the optical waveguide structure of the visible light modulator, Figure 3-Figure 6 shown.

[0104] Figure 3A cross-sectional view of an exemplary thin-film optical waveguide is given. In this structure, the electro-optic material film is an electro-optic crystal material bonded to a thin film substrate by ion slicing technology, such as LiNbO3 (lithium niobate), BaTiO3 (barium titanate), KTP (potassium titanyl phosphate), etc. In addition, the electro-optic material film can also be a thin film coating of LiNbO3, BaTiO3, KTP, etc. formed by a spin coating method, or a spin-coated electro-optic polymer. This diverse material selection allows the thin-film optical waveguide to adapt to different application requirements and provide efficient optical signal processing capabilities. The optical waveguide here adopts a heterogeneous ridge structure, which can be manufactured on the electro-optic material film by photolithography and etching technology. The protrusion structure formed on the electro-optic material film helps to effectively guide and limit the propagation of light waves in a specific area. After completing the manufacture of the heterogeneous ridge waveguide, an optional covering layer can be further prepared. This cladding layer usually uses a material with a lower refractive index than the electro-optical material, such as SiO2 or certain polymers, to ensure that the light waves are effectively confined and transmitted inside the ridge waveguide, thereby enhancing the overall performance and efficiency of the optical waveguide.

[0105] Figure 4 A cross-sectional view of another exemplary thin film light guide is shown. Figure 4 Another design of the exemplary thin film optical waveguide described in the present invention is shown. In this structure, the electro-optic material thin film can be an electro-optic crystal material bonded to a thin film substrate by ion slicing technology, such as LiNbO3 (lithium niobate), BaTiO3 (barium titanate), KTP (potassium titanyl phosphate), etc. In addition, the electro-optic material thin film can also be a thin film coating of LiNbO3, BaTiO3, KTP, etc. prepared by a sol-gel method formed by a spin coating method, or a spin-coated electro-optic polymer. Figure 3 The difference is that this design does not make ridge waveguides on electro-optical films, but forms shallow ridge waveguides on the electro-optical material film itself. This shallow ridge waveguide design helps to further optimize the transmission performance of light waves. It is also possible to further select the cover layer to reduce optical loss and optimize the speed matching between RF and optical signals.

[0106] Figure 5A cross-sectional view of another exemplary thin-film optical waveguide is given. In this structure, the thin-film optical waveguide is coated in a cladding layer on a thin-film substrate, and the refractive index of the cladding layer is slightly lower than that of the thin-film optical waveguide. The spacing between the thin-film optical waveguide and the electro-optical material film is very small, so that the optical mode field in the thin-film optical waveguide can be coupled to the electro-optical material film. This tightly coupled design not only ensures the efficient transmission of optical signals, but also maximizes the nonlinear optical properties of electro-optical materials. In a specific structure, different materials can be selected for the thin-film substrate to meet the requirements of mechanical strength and thermal expansion coefficient matching. The cladding layer is usually made of a material with a low refractive index, such as silicon dioxide (SiO2) or other suitable polymer materials, to ensure that the optical mode field in the thin-film optical waveguide can be effectively confined inside the waveguide.

[0107] Figure 6 A cross-sectional view of another exemplary thin-film optical waveguide is given. In this structure, the thin-film substrate is generally made of a material with good mechanical strength and thermal stability, such as silicon (Si) or other suitable materials. The thin-film substrate is covered with a first glass cladding layer prepared by a sol-gel method, which plays an optical isolation role to ensure that the optical signal in the thin-film optical waveguide is not absorbed or scattered by the substrate material. The thin-film optical waveguide is embedded in an electro-optic polymer layer prepared by a spin coating method. Through an annealing process, the optical properties of the electro-optic polymer layer can be further improved, and its stability and optical properties can be enhanced. The close coupling between the thin-film optical waveguide and the electro-optic polymer enables the optical mode field in the optical waveguide to be effectively coupled to the electro-optic material, thereby improving the transmission efficiency and modulation performance of the optical signal. The electro-optic polymer layer is covered with another Sol-Gel second glass cladding layer. Compared with traditional crystal and amorphous material modulators, the intrinsic low dielectric constant of the electro-optic polymer makes the microwave signal and the optical signal have similar refractive index, so that the speed mismatch between the two is almost negligible. This feature enables the device to achieve high-speed and broadband operation. With this design, the tight coupling between the thin-film optical waveguide and the electro-optic polymer enables the optical mode field to be effectively coupled into the electro-optic material, thereby improving the transmission efficiency and modulation performance of the optical signal.

[0108] Based on the above various optical waveguides, the improved visible light modulator of the present invention includes:

[0109] Modulator substrate,

[0110] A cladding layer is prepared on the modulator substrate and is used to cover the supporting thin film optical waveguide;

[0111] Thin film optical waveguide: coated in the above coating layer;

[0112] Electro-optical material film: bonded on the above-mentioned cladding layer, used to carry the coplanar waveguide electrode;

[0113] Coplanar waveguide electrode: attached to the thin film electro-optic material layer, modulating the optical signal by applying an electric field;

[0114] The distance between the thin film optical waveguide and the lower surface of the electro-optical material film is less than 100 nm.

[0115] The optical waveguides are as follows: Figure 7 As shown, this is based on Figure 5 The structure of the electro-optic material film is lithium niobate film as an example. This is a coplanar waveguide electrode structure of the Mach-Zehnder interferometer modulator. The SiN optical waveguide is coated in a coating layer of SiO2 material on the silicon substrate of the modulator made of Si. The spacing between the thin film optical waveguide and the thin film electro-optic material layer of thin film lithium niobate is very small (this spacing is controlled to be less than 100nm), so that the optical mode field in the optical waveguide can be coupled to the thin film electro-optic material layer. This tightly coupled design not only ensures the efficient transmission of optical signals, but also maximizes the nonlinear optical properties of electro-optical materials.

[0116] also, Figure 7 The signal electrode and the ground electrode are also shown. With this electrode structure, efficient modulation of the optical signal can be achieved. The coplanar waveguide electrodes are arranged on the two arms of the MZI modulator. By applying voltage, an electric field is generated between the electrodes, changing the refractive index of the electro-optical material (such as lithium niobate), resulting in a change in the phase in the two optical waveguide branches. By adjusting the applied voltage, the phase difference of the optical signal can be precisely controlled, thereby achieving modulation of the optical signal.

[0117] Figure 8 A three-dimensional schematic diagram of the visible light modulator provided by the present invention is given. A key challenge in efficient edge coupling of optical fiber to chip is the mode mismatch between the waveguide on the modulator chip and the optical fiber. For example, the present invention Figure 7The mode field diameter (MFD) of the design proposed in the patent is only a few hundred nanometers. In comparison, the MFD of common single-mode optical fibers in the visible light range is mostly around 3µm to 4µm, which results in significant mode mismatch losses when coupling light from the optical fiber. Although the MFD can be adapted by using a coupler with an inverse-tapered design, the tip width of such a design is extremely narrow, typically less than 50nm, and existing silicon photonics manufacturing plants have difficulty in reliably manufacturing such fine structures. To address this problem, this patent proposes the use of a double-layer edge coupler, which is designed with a minimum linewidth generally in the range of a few hundred nanometers and can be accurately and massively fabricated in a CMOS-compatible manufacturing environment. This double-layer design not only optimizes the mode conversion efficiency from optical fiber to thin-film optical waveguide, but also greatly reduces the losses caused by mode mismatch, thereby improving the performance and reliability of the overall system. In this design, the optical fiber is connected to the first inverse cone tip coupler, which gradually widens, and then the light passes through the gradual transition between the first inverse cone tip waveguide coupler and the second inverse cone tip waveguide coupler layer, so that the signal is transmitted to the straight waveguide whose width matches the thin film modulator optical waveguide through the evanescent wave. The second inverse cone tip coupler is directly prepared on the silicon substrate, the first inverse cone tip waveguide coupler and the second inverse cone tip waveguide coupler are wrapped in the cladding layer, and the thin film electro-optic material layer and the coplanar waveguide electrode are located on the upper surface of the cladding layer.

[0118] Fig. 9 The given is Figure 8 Side view of the visible light modulator.

[0119] In this view, the modulator substrate is a silicon substrate, a first inverse-tapered tip waveguide coupler and a second inverse-tapered tip waveguide coupler, and these two stages of couplers are designed to efficiently guide optical signals from an external light source into the optical waveguide of the modulator.

[0120] The cladding layer, whose main function is to protect the internal structure and provide necessary optical isolation to prevent optical signal leakage.

[0121] Thin films of electro-optical materials, as the primary medium in the modulation process, are able to control the phase and intensity of the optical signal passing through them through an applied electric field.

[0122] The coplanar waveguide electrode is used to apply an electric field to control the electro-optic effect of the electro-optic material, thereby realizing the modulation of the optical signal.

[0123] The visible light modulator further includes an optical splitter for distributing an input optical signal to a plurality of modulation channels. The optical splitter is an AWG demultiplexer suitable for a common wavelength multiplexing (CWDM) application.

[0124] At the same time, the visible light modulator also includes a plurality of photodetectors for monitoring the modulated light signal, and the photodetectors are arranged at the output end of each modulation channel. In addition, it also includes a radio frequency electrode and an MZI bias control electrode for applying a modulation voltage and providing a bias voltage respectively.

[0125] The above-mentioned visible light modulator further includes a covering layer covering the thin film electro-optic material layer and the coplanar waveguide electrode, wherein the material of the covering layer is silicon dioxide (SiO2) or polymer, so as to provide optical isolation and protection.

[0126] The visible light modulator of the present invention uses nonlinear materials such as lithium niobate (LiNbO3), potassium dihydrogen phosphate (KDP), potassium titanium phosphate (KTP) or barium titanate (BaTiO3) with excellent electro-optical effect, which effectively improves the modulation efficiency and response speed of the optical signal. In addition, the visible light modulator adopts a coplanar slot waveguide electrode structure, and slows down the propagation speed of the microwave signal through a periodic loading design to achieve speed matching between the radio frequency (RF) signal and the optical signal, thereby improving the bandwidth of the modulator. By adjusting the parameters of the slot, the RF parameters are optimized to ensure high modulation efficiency and impedance matching. The visible light modulator of the present invention significantly improves the speed matching between the RF signal and the optical signal, thereby greatly improving the bandwidth and modulation efficiency of the modulator.

[0127] The visible light modulator integrates an optical splitter and a monitoring photodetector to distribute the input optical signal to multiple modulation channels and monitor the modulated optical signal in real time. The optical splitter uses an arrayed waveguide grating (AWG) demultiplexer and is suitable for wavelength multiplexing (CWDM) applications, improving the flexibility and efficiency of the system.

[0128] In order to solve the mode mismatch problem between optical fiber and thin film optical waveguide, the present invention proposes a double-layer inverse tapered tip coupler design. This design can be accurately and massively manufactured in a CMOS-compatible manufacturing environment, optimizes the light coupling efficiency, and reduces the loss caused by mode mismatch. Specifically, this design solves the loss problem existing in traditional mode conversion, significantly improving the optical signal transmission efficiency and system reliability.

[0129] The heterogeneous integrated platform is used to integrate optical splitters and monitoring photodetectors to achieve efficient distribution and real-time monitoring of multi-channel optical signals, which is suitable for optical communication systems and optical computing equipment with high-density optical signal processing.

[0130] Fig.10 The given is Figure 7The optical mode field distribution of the visible light modulator at multiple different wavelengths (400nm, 650nm and 750nm). The advantage of this optical waveguide design is its wide wavelength adaptability, which enables one optical waveguide structure to cover applications in multiple wavelength ranges, simplifying the design and manufacturing process. From these optical mode field distribution diagrams, it can be seen that the same optical waveguide design is suitable for applications ranging from 400nm to 750nm. In addition, the tightly coupled structure improves the transmission efficiency and modulation performance of the optical signal, maximizes the nonlinear optical properties of lithium niobate, and is suitable for high-speed and broadband optical communication systems. Although the application shown here is in the visible light band, similar structures are also applicable to the optical communication band through simple parameter adjustments.

[0131] Fig.11 The relationship between the half-wave voltage (Vπ) and the modulator length (L) of this visible light modulator is shown in the figure, where Vπ (Vpi) is defined as the voltage when the optical path difference is half the wavelength.

[0132] For a device of length L, the formula used here to calculate Vπ at low frequency is:

[0133] Vπ=λ / [2Δn / V)L].

[0134] Clearly, for a given electrode and waveguide design, the required half-wave voltage decreases significantly as the modulator length increases. For example, when the modulator length is 0.4 cm, Vπ is 1.75 volts, while when the modulator length increases to 0.7 cm, Vπ drops to 1 volt.

[0135] However, increasing L also reduces the speed matching bandwidth, which is calculated as:

[0136] .

[0137] in,

[0138] is the effective refractive index in the RF mode,

[0139] is the effective refractive index of the optical mode.

[0140] Fig.12 The frequency response diagram of this visible light modulator is given in the ideal state with no RF loss and with load and signal source impedance matching.

[0141] The frequency response is m(f),

[0142] .

[0143] in:

[0144] is the effective refractive index in the RF mode,

[0145] is the effective refractive index of the optical mode,

[0146] L is the modulator length, which is 10 mm in the figure.

[0147] The speed of light.

[0148] The frequency response is mainly determined by the velocity mismatch between the RF signal and the optical signal. In the absence of velocity mismatch, m(f) = 1 and is independent of frequency. In this case, the bandwidth is ideally infinite. As can be seen in the figure, the difference in effective refractive index between the RF mode and the optical mode is .

[0149] When the effective refractive index difference Δn is 0.05, the 3dB bandwidth without RF loss is about 110GHz; when the effective refractive index difference Δn is 0.1, 0.2 and 0.5, the 3dB bandwidth is about 100GHz, 14GHz and 11GHz respectively. It can be seen that the effective refractive index difference has a significant effect on the bandwidth.

[0150] In summary, for optical modulators designed with bandwidths exceeding 100 GHz, the effective refractive index difference Δn between the RF mode and the optical mode should not exceed 0.05 to ensure sufficient bandwidth. This means that under high-frequency operation, the propagation speed matching of the RF and optical signals must be precisely controlled to reduce the bandwidth limitation caused by the speed mismatch. This is crucial for the development of high-speed optical communication systems and high-performance optoelectronic devices, as bandwidth directly affects signal transmission rate and system performance.

[0151] The electrode structure is a periodically loaded coplanar slot waveguide electrode; the coplanar slot waveguide electrode optimizes radio frequency (RF) parameters by adjusting slot parameters to ensure high modulation efficiency and impedance matching. Fig.13 The present invention provides a schematic diagram of a visible light modulator based on a coplanar slot waveguide electrode structure, specifically a Mach-Zehnder interferometer (MZI) modulator based on a coplanar slot waveguide electrode structure.

[0152] like Fig.13As shown, the optical waveguide is used to introduce and output optical signals. The core part of the modulator includes a pair of coplanar waveguide electrodes, where coplanar slot waveguide electrodes are used, and the coplanar waveguide electrodes include signal electrodes and ground electrodes. These electrodes are arranged on the surface of the electro-optical material to modulate the optical signal by applying an electric field on the material. Coplanar slot waveguide electrodes have been widely studied in III-V compound modulators, mainly used to slow down the speed of microwave signals. This design is usually implemented using a periodic loading structure, which is non-uniform along the propagation direction. The periodic T-shaped slots in the figure are an example, and other shapes of slots can be used in practical applications. These slots partially cut off the current path and increase the impedance and inductance of the electrode, thereby significantly slowing down the transmission speed of the electric wave in the waveguide and increasing the effective refractive index of the RF mode. Compared with traditional coplanar waveguides (CPW), by controlling the parameters of the slots, slot electrodes can adjust the radio frequency (RF) parameters while ensuring high modulation efficiency and impedance matching. The additional resistance and impedance generated by the slots are mainly determined by the size of the slots. In addition, the period of the slots needs to be carefully selected to ensure that the Bragg cutoff frequency is much higher than the operating frequency.

[0153] Fig.14 An equivalent circuit model of this coplanar slot waveguide design is presented, which helps calculate the characteristic impedance of the coplanar slot waveguide electrode structure and the microwave refractive index to match the effective refractive index of the optical mode.

[0154] Fig.15 The electro-optical response characteristics of the lithium niobate thin film optical waveguide modulator with different electrode designs are shown. In this figure, three coplanar waveguide electrode designs with different lengths and structures are compared: a 4mm coplanar slot waveguide electrode, a 7mm coplanar slot waveguide electrode, and a 7mm traditional coplanar waveguide (CPW, no slot).

[0155] By analyzing the electro-optical S21 parameters (transmission loss) of these designs at different frequencies, the diagram clearly shows the significant impact of the electrode structure on the performance of the modulator. As shown in the figure, the coplanar slot waveguide electrode exhibits low transmission loss over a wide frequency range, indicating that it has excellent electro-optical efficiency and is particularly suitable for high-frequency applications. In contrast, the traditional CPW has a low effective refractive index, which leads to poor speed matching between RF and optical signals, thereby reducing its electro-optical bandwidth and limiting its effectiveness in high-frequency applications. This figure clearly shows that by optimizing the length and structure of the electrode, the electro-optical response and overall performance of the modulator can be significantly improved, which is crucial for the design of high-efficiency and high-speed optical communication systems. The present invention achieves higher modulation efficiency and a wider operating frequency range by improving the strategy of electrode design, providing important technical support for the design of high-speed optical modulators.

[0156] It is obvious to those skilled in the art that the above embodiments are not intended to be exhaustive or limit the embodiments to the specific precise forms disclosed. It is obvious to those skilled in the art that certain modifications, combinations and variations can be made based on the above teachings.

Claims

1. A visible light modulator for high-speed optical communication and optical computing, characterized in that: include: The modulator substrate provides structural support and serves as an integration platform for the various optoelectronic components; A thin film optical waveguide layer, arranged on a modulator substrate, is provided with coplanar waveguide electrodes and modulates an optical signal by applying an electric field; An input optical waveguide, used for inputting an optical signal; an output optical waveguide for guiding the modulated optical signal; An optical distribution device, used for distributing an optical signal entering from an input optical waveguide to a plurality of modulation channels to achieve parallel processing; Several photodetectors are arranged at the output of each modulation channel to monitor the modulated optical signal and conduct real-time performance evaluation; A radio frequency electrode, applying a modulation voltage to control the electro-optical response characteristics of the electro-optical material; Bias electrodes, used to change the refractive index in the interferometer arms, adjust the optical path difference to achieve precise phase modulation and intensity regulation of the output signal, and balance the interferometer and adjust the bias point to ensure it operates at its optimal state; The thin film optical waveguide layer has an electro-optical material thin film for performing a modulation function of an optical signal, and its electro-optical response characteristics are controlled by a modulation voltage applied by a radio frequency electrode; It also includes a cladding layer, which is prepared on the modulator substrate and is used to clad the supporting thin film optical waveguide; Thin film optical waveguide: coated in the above coating layer; Electro-optical material film: bonded on the above-mentioned cladding layer, used to carry the coplanar waveguide electrode; Coplanar waveguide electrode: attached to the thin film electro-optic material layer, modulating the optical signal by applying an electric field; The distance between the thin film optical waveguide and the lower surface of the electro-optical material film is less than 100 nm.

2. The visible light modulator according to claim 1, characterized in that: The optical distribution device is an optical splitter or an array waveguide grating demultiplexer.

3. The visible light modulator according to claim 1, characterized in that: The coplanar waveguide electrode includes a signal electrode and a ground electrode.

4. The visible light modulator according to claim 1, characterized in that: The electrode structure of the coplanar waveguide electrode of the visible light modulator adopts a periodically loaded coplanar slot waveguide electrode structure.

5. The visible light modulator according to claim 1, characterized in that: The input optical waveguide and the output optical waveguide adopt a two-stage inverse tapered tip coupler for mode conversion.

6. The visible light modulator according to claim 5, characterized in that: The tip width of the inverse-tapered tip coupler is 100-700 nm.

7. The visible light modulator according to claim 1, characterized in that: The thin film optical waveguide layer has an electro-optical material film for performing a modulation function of an optical signal, and its electro-optical response characteristics are controlled by a modulation voltage applied by a radio frequency electrode.

8. The visible light modulator according to claim 1, characterized in that: The material of the optical waveguide in the thin film optical waveguide layer is silicon nitride, silicon or polymer.

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